Now that doesn't mean you can start laughing and drop your exercise program... but it does mean you can lighten up a lot, and get measurable health benefits.

A team from Vanderbilt University, Nashville, TN, has found that facial, respiratory and laryngeal muscles are all heavily used in genuine voiced laughter, leading to changes in lung volume and dynamic compression of the airways.

It's not the full-body workout provided by other forms of exercise, but the researchers suggest that a quarter hour of full-on laughter could equate to walking half a mile - which could take many people about the same amount of time. Call it laugh therapy, laugh medicine or straight out laughing fitness, this discovery quantifies the benefits of frivolity made famous by Norman Cousens in his Laughter is the Best Medicine book decades ago.

The Tennessee team also had this to say: "Other forms of more intense physical activity such as jogging, or household chores can increase EE (energy expenditure) by 100% or more.

"Therefore, although laughter cannot replace exercise or other forms of intense physical activity, its production should not be discounted in the total balance of energy and should be considered a component of the non-exercise activity thermogenesis.

"We have calculated that the energy cost of 15 minutes of laughter ranges from 40 to 170 kJ (10–40 kcal), depending on individual body weight and laughter intensity. This amount of energy expenditure during 1 year, with no changes in other components of energy balance, may translate into an annual weight loss of 0.5–2 km of body weight, if all other components of energy balance remained unchanged." Their full report is available here

In the meantime, anyone interested in a little laugh therapy of their own?